Apparatus for liquid treatment of wafer shaped articles and heating system for use in such apparatus

ABSTRACT

An apparatus for treating a disc-shaped article comprises a spin chuck and at least three individually controllable infrared heating elements. The infrared heating elements are mounted in a stationary manner with respect to rotation of said spin chuck. At least the transparent plate positioned between the infrared heating elements and the underside of a wafer is mounted for rotation with the spin chuck. Alternatively, the transparent plate is part of a housing that encloses the infrared heating elements and that rotates with the spin chuck as the heating elements are stationary relative thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an apparatus for liquid treatment ofwafer-shaped articles, and to a heating system for use in such anapparatus.

2. Description of Related Art

Liquid treatment includes both wet etching and wet cleaning, wherein thesurface area of a wafer to be treated is wetted with a treatment liquidand a layer of the wafer is thereby removed or impurities are therebycarried off. A device for liquid treatment is described in U.S. Pat. No.4,903,717. In this device the distribution of the liquid may be assistedby the rotational motion imparted to the wafer.

Techniques for processing a surface of a disc-shaped article aretypically used in the semiconductor industry on silicon wafers, forexample of 300 mm or 450 mm diameter. However, such techniques may beapplied for other plate-like articles such as compact discs, photomasks, reticles, magnetic discs or flat panel displays. When used insemiconductor industry they may also be applied for glass substrates(e.g. in silicon-on-insulator processes), III-V substrates (e.g. GaAs)or any other substrate or carrier used for producing integratedcircuits.

When using heated process liquids, there is a problem in achievingtemperature uniformity across the surface of the wafer, and the need toaddress that problem becomes more acute as wafer diameters increase.

In particular, as the wafer diameter increases, so too will thetemperature differential between a liquid at the point where it isapplied in a central region of the wafer and the same liquid after ithas travelled radially outwardly to the periphery of the wafer. Thisresults in varied etch rates as a function of the distance from thecenter of the wafer, and hence poor process uniformity.

Conventional approaches to alleviate this problem have includeddispensing process liquid from movable arms, so-called “boom swing”dispensers; however, this involves an increase in the cost andcomplexity of the device as well as its operation. The problem can beaddressed to some extent by increasing the flow of process liquid,and/or by dispensing a high temperature liquid such as deionized wateron the opposite side of the wafer; however, these techniques result inhigher consumption of process liquids.

U.S Patent Application Pub. No. 2013/0061873 describes improvedapparatus equipped with an infrared heater for heating a wafer toenhance process uniformity. Although the devices of that patentapplication represent an improvement over conventional techniques, thereremains a need to provide further enhanced process uniformity andequipment that is more robust and easier to maintain.

SUMMARY OF THE INVENTION

Thus, in one aspect, the present invention relates to an apparatus fortreating a wafer-shaped article, comprising a spin chuck for holding awafer-shaped article in a predetermined orientation wherein a lowersurface of the wafer-shaped article is spaced a predetermined distancefrom an upper surface of the spin chuck. At least one infrared heater ismounted above the upper surface of the spin chuck and underlying awafer-shaped article when mounted on the spin chuck, the at least oneinfrared heater being stationary in relation to rotation of the spinchuck. A plate that is transparent to infrared radiation emitted by theat least one infrared heater is mounted for rotation with the spin chuckand positioned between the at least one infrared heater and awafer-shaped article when positioned on the spin chuck.

In preferred embodiments of the apparatus according to the presentinvention, the plate is part of a housing that surrounds the at leastone infrared heater, the housing being mounted for rotation with thespin chuck.

In preferred embodiments of the apparatus according to the presentinvention, the housing comprises a lower shell surrounding the at leastone infrared heater and positioned between the at least one infraredheater and the upper surface of the spin chuck, the lower shell having areflective interior surface.

In preferred embodiments of the apparatus according to the presentinvention, the spin chuck comprises a rotatable chuck body surrounding acentral stationary post, and the at least one infrared heater is mountedto an upper end of the central stationary post.

In preferred embodiments of the apparatus according to the presentinvention, the at least one infrared heater is part of a heatingassembly comprising at least two, and preferably at least three,independently controllable infrared heating elements.

In preferred embodiments of the apparatus according to the presentinvention, the housing is centered on an axis of rotation of the spinchuck, and the spin chuck comprises a circular series of pins configuredto contact an edge of a wafer-shaped article in a closed position, thepins passing through a corresponding series of openings formed in aperiphery of the housing.

In preferred embodiments of the apparatus according to the presentinvention, each of the independently controllable heating elementscomprises at least one curved portion.

In preferred embodiments of the apparatus according to the presentinvention, a lower shell surrounds the at least one infrared heater andis positioned between the at least one infrared heater and the uppersurface of the spin chuck, the lower shell having a reflective interiorsurface and being stationary in relation to rotation of the spin chuck.

In another aspect, the present invention relates to an infrared heatingassembly for use in an apparatus for treating a wafer-shaped article.The infrared heating assembly comprises a housing comprising an upperplate that is transparent to infrared radiation emitted by the infraredheating assembly, and a lower shell having a reflective interiorsurface. A plurality of infrared heating elements is mounted on a commonframe positioned with the housing, the common frame comprising aconnector portion projecting downwardly through a central opening in thelower shell. A rotary bearing is positioned outside of the connectorportion and inside of the central opening, thereby to permit rotation ofthe housing relative to the common frame and the plurality of infraredheating elements.

In preferred embodiments of the infrared heating assembly according tothe present invention, each of the infrared heating elements isindependently controllable and comprises at least one curved portion.

In preferred embodiments of the infrared heating assembly according tothe present invention, the curved portions of adjacent infrared heatingelements extend along concentric circles.

In preferred embodiments of the infrared heating assembly according tothe present invention, the connector portion comprises a plurality ofelectrical connectors equal in number to the plurality of infraredheating elements, thereby to permit individual connection of each of theplurality of infrared heating elements to a controller for individuallyenergizing each of the plurality of infrared heating elements.

In preferred embodiments of the infrared heating assembly according tothe present invention, the housing is rotatable relative to the commonframe and the plurality of infrared heating elements about an axis thatis perpendicular to the upper plate.

In preferred embodiments of the infrared heating assembly according tothe present invention, each of the infrared heating elements comprisesat least one curved portion, and the at least one curved portion of eachof the infrared heating elements extends along an arc of a circle whosecenter is offset from the axis.

In preferred embodiments of the infrared heating assembly according tothe present invention, the housing comprises a circular series ofperipheral openings to permit passage of gripping pins when the infraredheating assembly is mounted to a spin chuck.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the invention will become moreapparent after reading the following detailed description of preferredembodiments of the invention, given with reference to the accompanyingdrawings, in which:

FIG. 1 is an exploded perspective view of an apparatus for treatingdisc-shaped articles according to an embodiment of the presentinvention;

FIG. 2 is top plan view of the embodiment of FIG. 1;

FIG. 3 is an axial section through the chuck depicted in FIGS. 1 and 2,taken along the line III-III of FIG. 2;

FIG. 4 is an enlarged view of the detail IV designated in FIG. 3;

FIG. 5 is an enlarged view of the detail V designated in FIG. 3; and

FIG. 6 is an axial sectional view similar to that of FIG. 3, of anotherembodiment of an apparatus for treating disc-shaped articles accordingto the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings, FIGS. 1 and 2 depict an apparatus made upof two principal subassemblies, namely, a base spin chuck 10 and amodular infrared heating assembly 20. The spin chuck 10 comprises arotary main body 12 that is mounted for rotation about a stationarycentral hollow post 14. This post 14 in turn comprises a central nozzle18 for dispensing process liquid or gas onto the underside of a waferwhen mounted on the spin chuck, as well a series of female electricalsockets 15 in a shoulder of the post 14, which sockets receivecorresponding male connectors (not shown) that depend downwardly fromthe heating assembly 20, and which supply driving current to the IRheating lamps inside that assembly 20.

The chuck body 12 has mounted therein a series of gripping pins 16,which operate generally as described in the above-referenced U.S. Pat.No. 4,903,717, in that the pins 16 are driven in unison by a common ringgear between a radially outer open position and a radially inner closedposition in which the upper ends of these pins engage the edge of adisc-shaped article to be treated. Chuck body 12 also includessmooth-walled bores 13 that receive corresponding positioning bosses(not shown) that depend downwardly from the heating assembly 20, so asto aid in positioning and supporting the heating assembly 20 in itscorrect orientation relative to the chuck body 10.

The heating assembly 20 in this embodiment is formed as a modular unitcomprising a lower dished housing or shell 22 that contains the IR lamps21, 23, 25. A cover 24 is screwed onto the lower housing 22 by a seriesof peripheral screws 26, which are six in number in this embodiment.Screws 26 alternate with six notches or openings 17 that pass entirelythrough the heating assembly 20 from top to bottom, and which permitpassage of the gripping pins 16. The broken line in FIG. 1 designatesthe position of a wafer W when held by the apparatus, in which positionthe wafer is supported at its peripheral edge by the distal ends of thegripping pins 16 projecting upwardly through the through bores ornotches 17, with the underside of wafer W being spaced by a smalldefined gap from the cover 24.

The cover 24 in this embodiment is a plate formed from a material thatis transparent to the wavelengths of IR radiation emitted by the lamps21, 23, 25, and this plate 24 may be formed for example of sapphire orquartz glass, as is known to those skilled in this art. The plate 24 hasa small central opening 19 formed therein, to permit passage of theupper end of dispensing nozzle 18.

Within the housing of the heating assembly 20, that is, inside the lowerhousing 22 and beneath the transparent plate 24, there is mounted a setof three infrared heating lamps 21, 23, 25, which are carried by acommon frame 29 that also incorporates the associated electrical supplywiring (not shown). The assembly formed by frame 29 and lamps 21, 23, 25in this embodiment is rigidly mounted to the stationary post 14, whereasthe housing formed of lower shell 22 and upper plate 24 is rigidlymounted to the rotary chuck body 12. Therefore, the frame 29 and thusalso the lamps 21, 23, 25 that it carries are mounted for rotationrelative to the surrounding housing formed of components 22, 24, as willbe described in greater detail below.

Referring now to FIG. 2, it can be seen that the wafer W is nowsupported by the ends of pins 16 projecting through the openings ornotches 17 in the heating assembly 20. The wafer W is centered on theheating assembly 20, which in turn is centered on the axis of rotationof the underlying spin chuck. It will be appreciated that the spin chuck10 is therefore designed to hold a wafer W of a specified diameter. Inthe embodiments described herein, that diameter is 300 mm, which is acommon diameter of silicon wafer at present. However, the apparatus mayof course be designed to hold disc-shaped articles of other diameters,such as 200 mm and 450 mm.

In the plan view of FIG. 2 it can be seen that each of the three heatingelements 21, 23, 25 in this embodiment is a continuous curved tubularelement. Moreover, while these heating elements generally follow acircular arc, and while all three heating elements are preferablysubstantially concentric, the circles described by those heatingelements are not in this embodiment concentric with the center of theheating assembly 20 and hence are not concentric with the axis ofrotation of the spin chuck.

Consequently, in this embodiment, both the position and shape of theheating elements 21, 23, 25 is such that, as the wafer W is rotated bythe chuck 10 relative to the stationary heating elements 21, 23, 25,each heating element effectively “travels” radially relative to therotating wafer W, in that each heating elements heats an annular regionwhose radial extent is significant greater than the cross-sectionaldiameter of the heating elements.

In FIG. 3, it can be seen that the frame 29 is supported within thehousing 22, 24 by a suitable rotary bearing 33, which permits thehousing of the heating assembly 20 to rotate relative to the stationarypost 14 with the frame 29 and lamps 21, 23, 25 being mounted in astationary manner to the post 14. The upwardly-facing surface of thelower housing part or shell 22 is preferably provided with a suitable IRreflective coating 31, to aid in directing the IR radiation emitted bylamps 21, 23, 25, upwardly through the transparent plate 24 and onto thedownwardly facing surface of the wafer W.

The stationary post 14 is mounted onto the frame 32 of the apparatus,which in this embodiment also carries a stator 34. Stator 34 in turndrives rotor 36, which is attached to the body 12 of spin chuck 10. Alsovisible in FIG. 3 is the ring gear 11 mentioned above, which drives thegripping pins 16 in unison.

FIG. 4 shows an inlet 37 into the frame 29 and communicating with anoutlet of the post 14, which permits the interior of the heatingassembly 20 to be purged for example with nitrogen gas. Also shown inFIG. 4 is a conduit 35 that opens on a shoulder of the post 14, and intothe small gap 39 defined between the upper surface of the chuck body 12and the lower surface of the housing shell 22. Conduit 35 can beadvantageously used to supply deionized water to the gap 39, so as tocool the heating assembly 20 upon completion of a heating operation, aswell as to regulate the temperature generated by the heating assemblyduring a heating operation.

Visible in FIG. 5 is a gap 41 provided between the transparent cover 24and the lower shell housing 22, which permits nitrogen purge gasintroduced into the housing to be exhausted outwardly therefrom.Similarly, gap 43 shown in FIG. 5 permits the escape of the deionizedwater (or, if desired, nitrogen gas) that had been introduced into thegap 39 between the bottom of shell 22 and the upper surface of chuckbody 12.

In the alternative embodiment of FIG. 6, the transparent plate 24′ stillrotates with the spin chuck 10, and pins 16′ still pass upwardly throughopenings formed in the transparent plate 24′. However, the lower shell22′ of this embodiment is now rigidly secured to the post 14 in acantilever manner, along with the frame 29 and lamps 21, 23, 25. Thisembodiment is otherwise as described above in connection with thepreceding embodiment.

It is advantageous for the transparent plate 24, 24′ to rotate with thespin chuck 10 as in these embodiments, because any droplets of processliquid adhering to the transparent plate 24, 24′ will thereby be spunoff. However, in a still further embodiment, the entire heating assemblymay be mounted in a stationary manner on the post 14, as is describedfor example in connection with the heating assembly disclosed incommonly-owned co-pending application U.S Patent Application Pub. No.2013/0061873.

It is to be noted that the heating lamps in each of the precedingembodiments are preferably individually controllable. It is particularlypreferred that each lamp can be not only switched on and offindependently of the others, but also that the wattage to each lamp canbe independently varied. This permits a variety of advantageous processcontrol.

While the present invention has been described in connection withvarious preferred embodiments thereof, it is to be understood that thoseembodiments are provided merely to illustrate the invention, and shouldnot be used as a pretext to limit the scope of protection conferred bythe true scope and spirit of the appended claims.

What is claimed is:
 1. Apparatus for treating a wafer-shaped article,comprising: a spin chuck for holding a wafer-shaped article in apredetermined orientation wherein a lower surface of the wafer-shapedarticle is spaced a predetermined distance from an upper surface of thespin chuck; at least one heater mounted above said upper surface of saidspin chuck and underlying a wafer-shaped article when mounted on thespin chuck, said at least one heater being stationary in relation torotation of said spin chuck; and a plate that is transparent toradiation emitted by said at least one heater, said plate being mountedfor rotation with said spin chuck and being positioned between said atleast one heater and a wafer-shaped article when positioned on said spinchuck.
 2. The apparatus according to claim 1, wherein said plate is partof a housing that surrounds said at least one heater, said housing beingmounted for rotation with said spin chuck.
 3. The apparatus according toclaim 2, wherein said housing comprises a lower shell surrounding saidat least one heater and positioned between said at least one heater andsaid upper surface of said spin chuck, said lower shell having areflective interior surface.
 4. The apparatus according to claim 1,wherein said spin chuck comprises a rotatable chuck body surrounding acentral stationary post, and wherein said at least one heater is mountedto an upper end of said central stationary post.
 5. The apparatusaccording to claim 1, wherein said at least one heater is part of aheating assembly comprising at least two independently controllableheating elements.
 6. The apparatus according to claim 2, wherein saidhousing is centered on an axis of rotation of said spin chuck, andwherein said spin chuck comprises a circular series of pins configuredto contact an edge of a wafer-shaped article in a closed position, saidpins passing through a corresponding series of openings formed in aperiphery of said housing.
 7. The apparatus according to claim 5,wherein each of said independently controllable heating elementscomprises at least one curved portion.
 8. The apparatus according toclaim 1, further comprising a lower shell surrounding said at least oneheater and positioned between said at least one heater and said uppersurface of said spin chuck, said lower shell having a reflectiveinterior surface and being stationary in relation to rotation of saidspin chuck.
 9. The apparatus according to claim 1, wherein said at leastone heater is part of a heating assembly comprising at least threeindependently controllable heating elements.
 10. A heating assembly foruse in an apparatus for treating a wafer-shaped article, said heatingassembly comprising: a housing comprising an upper plate that istransparent to radiation emitted by said heating assembly, and a lowershell having a reflective interior surface; a plurality of heatingelements mounted on a common frame positioned within said housing, saidcommon frame comprising a connector portion projecting downwardlythrough a central opening in said lower shell; and a rotary bearingpositioned outside of said connector portion and inside of said centralopening, thereby to permit rotation of said housing relative to saidcommon frame and said plurality of heating elements; wherein saidhousing is rotatable relative to said common frame and said plurality ofheating elements about an axis that is perpendicular to said upperplate.
 11. The heating assembly according to claim 10, wherein each ofsaid heating elements is independently controllable and comprises atleast one curved portion.
 12. The heating assembly according to claim11, wherein the curved portions of adjacent heating elements extendalong concentric circles.
 13. The heating assembly according to claim10, wherein said connector portion comprises a plurality of electricalconnectors equal in number to said plurality of heating elements,thereby to permit individual connection of each of said plurality ofheating elements to a controller for individually energizing each ofsaid plurality of heating elements.
 14. The heating assembly accordingto claim 10, wherein each of said heating elements comprises at leastone curved portion, and wherein said at least one curved portion of eachof said heating elements extends along an arc of a circle whose centeris offset from said axis.
 15. The heating assembly according to claim10, wherein said housing comprises a circular series of peripheralopenings to permit passage of gripping pins when said heating assemblyis mounted to a spin chuck.
 16. A heating assembly for use in anapparatus for treating a wafer-shaped article, said heating assemblycomprising: a housing comprising an upper plate that is transparent toradiation emitted by said heating assembly, and a lower shell having areflective interior surface, said housing comprising a circular seriesof peripheral openings to permit passage of gripping pins when saidheating assembly is mounted to a spin chuck; a plurality of heatingelements mounted on a common frame positioned within said housing, saidcommon frame comprising a connector portion projecting downwardlythrough a central opening in said lower shell; and a rotary bearingpositioned outside of said connector portion and inside of said centralopening, thereby to permit rotation of said housing relative to saidcommon frame and said plurality of heating elements.
 17. The heatingassembly according to claim 16, wherein each of said heating elements isindependently controllable and comprises at least one curved portion.18. The heating assembly according to claim 16, wherein said connectorportion comprises a plurality of electrical connectors equal in numberto said plurality of heating elements, thereby to permit individualconnection of each of said plurality of heating elements to a controllerfor individually energizing each of said plurality of heating elements.19. The heating assembly according to claim 16, wherein said housing isrotatable relative to said common frame and said plurality of heatingelements about an axis that is perpendicular to said upper plate. 20.The heating assembly according to claim 18, wherein each of said heatingelements comprises at least one curved portion, and wherein said atleast one curved portion of each of said heating elements extends alongan arc of a circle whose center is offset from said axis.